Parabolic-mirror-grinding machine.



T. A. CORRY.

PARABOLIQ MIRROR emuoma MACHINE.

A PfL ILC ATION FILED bar. 16. 1914,

Patented Feb. 8,1916.

3 SHEETS-SHEET 1.

.- IMIENTIOR WITNESSES 4 rrnn s'rarits rnrnn'r enrich THOMAS AVERYCURRY, OFIAREQUIPA, PERU.

IPARABOLIG-MIB-BOR-GRINDING MACHINE.

Specification of Letters Patent.

Application filed (ictobe'r 16, 1914. Serial No. 866,952.

To all whom it may concern Be it known that I, THOMAS A. Corny, acitizen of the United States, and a resident of Arequipa, Peru, haveinvented a new and Improved Parabolic-Mirror-Grinding Machine, of whichthe'following is a full, clear, and exact description.

This invention relates to machines or apparatus forthe manufacture andfinishing of optical lenses or special forms of reflecting mirrors, andhas particular reference to machines for concaving and polishingparabolic reflecting mirrors such as are used particularly 1nreflecting'telescopes, headlights, etc.

. Among the objects of the invention is to provide a device of apractical and reliable nature and which, when once adjusted, is adaptedto operate practically automatically for the" purpose ofgrinding orconcaving a piece of work-and which produces a concavity substantiallyparabolic within the practical range of the machine.

The'foregoing and other objects of the invention will hereinafter bemore fully described and claimed and illustrated in the drawings forminga part of this specification in which like characters of referenceindicate corresponding parts in all the views,

and in which- Figure 1 is a front elevation of a preferred embodiment ofthe machine, parts being in section; Fig. 2 is a side view of the same,also partly in section; Fig. 3 is a view corresponding, to the upperportion of Fig. 2 but indicating a modified form of counter balancingmeans for the grinding tool; Fig.

-4 is a modification of the lower portion of Fig. 1 indicating onepreferred form of mechanism for manipulating the grinding instrumentautomatically, and Fig. '5 is a vertical section of the central part ofFig.

1 on a plane parallel to that of Fig. 1.

The several parts of the device may be made of any suitable materials,and the relative sizes and proportions, as well as the general design ofthe mechanism, may be varied to a considerable extent without departingfrom the spirit of the invention hereinafter more fully set forth andspecifically claimed. I

Referring more particularly to the drawings, I show a main framecomprising prac-' ticall-y three legs or standards 10 having their feetconnected at 11 to a base 12 adapted to besupported in any suitablemanner in afsubstantially horizontal position. The

upper ends of the legs are secured to an annulus or collar 13 having anopen center and. arranged in a substantially horizontal plane. The twoside legs are arranged substantially diametrically opposite from eachother and the other leg is arranged in the rear thereof,

Patented Feb. 8, 1916.

leaving the front of the machine free for the mounting and operation ofthe active portions thereof.

At 14 I show a vertical rotary tool shaft supported substantiallycentrally with respect to the annulus 13 within which the shaft isadapted to oscillate in a plane parallel to the vertical plane of thetwo side legs 10 and around an axis extending through the annulus 13from front to rear.

The shaft 14 is journaled at its upperend in a clamp 15 and a sleevel6projecting upwardly therefrom. The clamp is provided at the front andrear with a pair of arms 17 having cone bearing connections with a pairof adjustment screws 18 extending-hori-.

zontally through the annulus.

A suspension rod 19 is connected at its upper end to the clamp 15 and atits lower end is fitted loosely in a bearing block 20.

A block 21 is secured to the rod 19 aboveits.

lower end. The shaft 14 is journaled in the blocks 20 and 21 but is freeto slide verti cally within said blocks.

22 indicates a suitable grinding or polishing tool adjustably fitted tothe lower end;

is journaled antifrictionally by means of collars 24 and 25' secured tothe shaft and between which collars and the sleeve bearing balls arelocated. An arm 26 is secured to the sleeve 23 and projects lateralltherefrom, the arm having a' surface 2 along its lower edge which issubstantially perpendicular to the axis of the shaft. A. slide 27 bearsupwardly against the'surface 26 of ';the arm and said slide is journaledupona' horizontal axis 28 extending between pairs of pantographie armsor toggle links 29' and 30, the pivot oraxis passing through selectiveholes formed in the links '29, whereby the relative lengths of the links29 and 30 may be varied. The upperends of the links 29 are pivoted at 31to the clamp 21 and the lower ends of the lower links 30 are pivoted at32 to the end of an arm 33 secured rigidly to and carried by a slide 34movable preferably in a straight horizontal line along a 'bar 35supported upon the side legs 10 and constituting what may be termedadirectrix. It will be .understood that the toggle links 29 and 30,together with the slide 27, constitute the main support for the arm 26and rotary shaft 14 and hence these elements constitute a stop limitingthe downward movement of the shaft and the tool secured thereto.

The action of gravity upon the shaft 14 and parts carried thereby iscounteracted to a greater or less extentby any suitable counterpoisedevices. As shown in Fig. 1,

there is'e'mployed a coil spring 36 acting upwardly upon the shaft andsupported upon the clamp 21. The effect of the spring is variable byvirtue of'a winged nut 37 at the upper end of the spring. In Fig. 3,however, is shown another counterpoisedevice which comprises a weightpan '38 having a flexible connection 39 leading therefrom over directionpulleys 40 to a swivel 41. connected to the upper end of the shaft 14.

The adjustment of the effect of gravity upon the shaft and tool isnecessary particularly in the finishing of a lens or mirror.

The slide 34 is adapted to be operated along the directrix by anysuitable means, either by hand applied to a handle 42 or by means ofmechanical devices such as shown in Fig. 4. In this figure is shown across head 43 slidable along guideways 44 extending horizontally andoutwardly from one ofsary or advisable according to the diameter of themirror or lens operated upon or in ac-' cordance with the amplitudeofmovement of the tool 22. The axis 31 pertaining to 1 the upper pivotsfor the links 29 carried by the clamp 21 bearsa constant'relation totheaxis 17 around which the operating parts oscillate, and hence, asshown in Fig. 1, the

point 31 must swing in the arc of a true circle. The point 32 bearinga'constant fixed relation to .the slide 34 must move in a straighthorizontal line or a line parallel to the directrix. It follows,therefore, that when the slide is'moved in either direction .theconcavity is deepened or the curve from the normal or mid position shownin full lines in Fig. 1, the two points 31 and 32 move apart. Since thelinks 29 and 30 are pivoted together on the point or axis 28 and havetheir opposite ends pivoted to the points 31 and 32, it follows that thepoint 28 is caused by the oscillation of the shaft to describe a curveof a character intermediate the straight line described by the point 32and an arc of acircle described by the point 31. The slide 27 carried-bythe axis 28 will therefore define or determine the path of movement ofthe tool 22 by reason of its cooperation with the arm 26 and sleeve 23supporting the shaft 14.

With the parts arranged and proportioned substantially as indicated inFig. 1, the path of movement of the active point of the abrading tool 22is substantially a true parabola within the practical arc ofoscillation, the focal center of the parabolic curve coinciding with theaxis of oscillation of the shaft 14.' It is obvious, however, that theform of the curve may be variedby variously adjusting the relationbetween the several points indicated. For instance,bylowering the point28, a flatter concavity will be produced, and by increasing the distancebetween the point of the tool and the point 32,

formed by the tool is sharpened.

The plate or job being treated and shown at 53 is supported in operationupon a turn- .table 54 secured to a spindle 55 preferably of conicalform and journaled in a bearing 1 0 socket Said socket and parts carriedtherein are adjustable vertically by means of a set screw 5'? operatingthrough the bottomof a casing or holder 58 shown .assecured to thecentral portion of the bed plate 12. The turntable may be caused torotate at any desired speed and by any suitable means. I prefer,however, to rotate itcomparatively slowly by means of a worm 5900operating with teeth 60 formed upon the periphery of the turntableandthereby constituting the turntable as a worm gear. The worm 59 is-shownas mounted upon a shaft 61 which is driven by miter gears 62 from avertical power shaft 63 journaled in the mainframe of the machine. Amain driving wheel 64 is secured to the shaft 63 and may be operatedbymeans of a belt 65., To the upper end of the shaft 63 is secured abelt wheel 66 having a belt 67 leading there- 129 from to a'small pulley68 journaled upon the aforesaid bearing sleeve 16. Pins 69 and 76carried by the pulley and shaft 14 respectively serve to insure therotation of the shaft from. the pulley while allowing a comparativelyfree slidable movement of the shaft. .1 The pin 70 is connected toa-collar '71 rigidly secured tothe upper end ofthe Qshaft. By virtue ofthe sleeve 16' the strain of the belt 67 upon the pulley is relievedfrom the shaft and hence all unnecessary friction between the shaft andits bearings 1s prevented.

Having thus described my invention, I claim as new and desire to secureby Letters Patent 1. In a machine of the character set forth, thecombination of a support, a suspension member mounted upon a horizontalpivot in said support and adapted to oscillate around its pivot, arotary shaft arranged in said suspension member and adapted to oscillatetherewith, means to rotate the shaft, a tool carried by the free end ofthe shaft, and means cooperating with the suspension member and therotary shaft serving to cause the active point of the tool to describeda parabolic curve while the suspension member oscillates in the arc of acircle.

2. In a device of the character set forth, the combination of a rotaryshaft, means to support the shaft for oscillation around a fixed axisbut allowing theshaft to slide transversely of said axis, means torotate the shaft in its support, a tool carried by the free end of theshaft, and means cooperat- I ing with the shaft and its supporting meansserving to cause the point of the tool to describe a parabolic curvewhose. focal center cfiiricides with'the axis of oscillation of the s at.

3. In a machine of the character set forth, the combination of a mainsupporting frame including a horizontal annulus adjacent its top, arotary shaft extending centrally of said annulus, means pivotallysupporting the shaft on a fixed axis in said annulus and permitting theoscillation of the shaft around said axis, said shaft supporting meansincluding a rigid member adapted to swing with the shaft in an arc of acircle,

a tool secured to the free end of the shaft, a rigid stationary memberadjacent the plane of oscillation of the shaft, a slide movable to andfro on said stationary member along a path different from an arc of acircle, and means connected to said slide and cooperating with the shaftand its supporting means serving to cause the tool to describe a pathhaving a form differing from both the path of theslide and an arc of acircle.

4. In a machine of the character set forth, the combination of asupporting frame ineluding a horizontal annulus, rotary shaft supportingmember for the shaft including bearing arms journaled in a. horizontalaxis in the annulus and including bearings in which the shaft rotates,every point of the rigid supporting member being adapted to oscillate inan arc of a circle around the pivotal axis of the shaft, a tool carriedby the free end of the shaft and movable with the shaft longitudinallyin its bearings, a rigid stationary member arranged transverse to thenormal mid-position of the shaft, a slide fitted to the stationarymember and movable to and fro thereon and describing a path differingfrom an arc of a circle, a pair of members pivoted together and havingtheir opposite ends pivoted respectively to the rigid shaft supportingthe said slide, and means cobperatmg with said pair of members and theshaft serving to cause the tool to describe a path differing both fromthat of the slide and an arc of a circle, substantially as set forth.

5. In a machine of the class set forth, the combination of a mainsupport, a rotary shaft, means to support the shaft in themain-suppo'rtfor-oscillation around a horizontal axis, said shaft support includingbearing members in which the shaft is jou'rnaled and adapted to slidelongitudinally, a tool carried by the free end of the shaft, a

rigid stationary member adjacent the path caused to describe a paraboliccurve simultaneously with the operation of the shaft and support.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

. THOMAS AVERY COREY.

Witnesses:

G. G. STAFFORD, R. N. STAFFORD.

